Patent GB-199839-A (GB)
Abstract: 199,839. Western Electric Co., Ltd., (Western Electric Co., Inc.). April 3, 1922. Automatic and semi-automatic exchange systems.-In a small private branch exchange containing three groups of subscribers' lines, local connections within the P.B.X. are extended over non-numerical relay switching-arrangements shown in the lower half of Fig. 2 to an idle link circuit, Fig. 3, and completed over group and units connecting-relays CG, CU both of which are selected by the same unimotional marking switch, the wipers of which are stepped forward consecutively by both digits of the called number. The subscribers' lines are allotted numbers 11 - - 18, 21 - - 27, 31 - - 36, the first three contacts of the wiper 221 of the marking switch leading to group relays CG, one of which locks up in response to the first digit, whilst the second to the ninth contacts of a second wiper 219 lead to units relays CU. With this arrangement, the number of the contact set reached by the wiper 219 is the sum of the digits of the wanted number, each such contact set, for example the fourth, having associated with it three lines, Nos. 13, 22 and 31, the particular line of these three with which connection is established being dependent upon whether the wipers have reacted their fourth contacts in a succession of one plus three steps, two plus two steps or three plus one steps respectively. The switch-over from wiper 221 to wiper 219 at the end of the first digit is controlled by a, relay 309, Fig. 3, energized during the digit and de-energized at the end of it. The non-numerical switching-arrangements also comprise group and units connecting- relays 206, 208 the operation of which is completely controlled by a single armature and contact of a line relay 201. Certain subscribers may obtain connections to a main exchange by dialling the single digit O in which case none of the group relays CG are energized but a relay 214 initiates the operation of the relay arrangements shown in Fig. 1 by which the calling line is connected directly over group and units connecting-relays 103, 105 to an idle trunk, Fig. 4, the link circuit, Fig. 3, being released. The trunk shown serves for both outgoing and incoming connections, a relay 101 which connects the starting circuit 235 to the next idle trunk being operated immediately upon the initiation of an incoming call, but being prevented from operating in the case of an outgoing call, until after the operation of the connecting relays 103, 105. In the case of an outgoing call to a main automatic exchange. impulses transmitted by the calling subscriber are repeated by a relay 407 to the main exchange, part of which is shown in the dotted rectangle, Fig. 5, whilst means are provided comprising an auxiliary switch, Fig. 5, also operated by the impulses, which can be set so that on the dialling of numbers containing predetermined combinations of digits, a lamp 439, Fig. 4, is lit in order that calls to such numbers may be supervised by an operator. Incoming calls from a manual main exchange are completed at the P.B.X. by an operator, who, on observing lamp 439 which lights in response to the transmission of ringing- current over the trunk, completes the connection by depressing a key 453 individual to the wanted subscriber. No. 14, say, so energizing relays 112, 103. Local calls; connection to idle link circuit, Fig. 3. When calling subscriber No. 13 removes his receiver, line relay 201 completes a circuit for a group relay 202 in series with a pilot relay 204 which energizes a relay 205 and a slowrelease relay 301, both individual to the first idle link circuit. Relay 205 energizes group and units connecting-relays 206, 20S which lock up over conductors 307, 302 and connect the selected link-circuit to the calling substation, in series with which relay 303 energizes. Relay 209 energizes over conductor 304 and transfers the starting circuit 216 over conductor 217 to the back contact of a similar relay 209 in the next idle link circuit. Relay 301 energizes the cut-off relay 213 over the grounded lead 302 and completes a circuit 302, 310. 219, 220 for relay 309 which energizes and locks up over conductor 311 to disconnect wiper 219, and to ground wiper 221. Completion of connection to wanted line (No. 31). When the calling subscriber dials the first digit, the de-energization of relay 303 at each impulse removes a short-circuit from relay 313 which responds to energize a slow-release relay 308 and to repeat the impulses to stepping magnet 222 by which the wipers are moved to their third contacts. Upon the relapse of relay 308 at the end of the digit, group relay 223 energizes over the circuit 221, 311, 302 and locks up, whilst, shortly afterwards, relay 309 deenergizes to transfer the grounded lead 302 to the other wiper 219. Relay 313 responds in the same way to the single impulse of the second digit by which the wipers are moved to their fourth contacts, and when, at the end of the digit, relay 308 relapses, units relay 224 is energized over the circuit 219, 310, 302 and locks up thus completing the connection of the link circuit, Fig. 3, to the wanted line. Busy test and release. The slow-release test relay 315 is energized by relay 308 during the transmission of the second digit and connects the left-hand winding of relay 306 to the test lead 227. If the called line is busy, the ground connection on lead 227 energizes relay 306 which locks up and energizes relay 316. As soon as connection was made to the link circuit, a tone signal from a source 317, was transmitted over condjenser 319 to the calling subscriber, first acting as a dialling signal, but the persistence of this tone after the completion of dialling serves as a busy signal, since, if the called line is idle, the source 317 is cut off by the operation of relay 318 referred to in the next paragraph. When the calling subscriber hangs up, the relapse of relay 303 de-energizes relays 209, 301 the latter of which removes ground from conductor 302 so releasing all the other relays. Switch wipers 219, 221, which are held in their operated position by relay 301, also restore to normal when this relay is de-energized. Ringing arrangements. If the called line is idle, relay 306 does not energize over its left-hand winding, but, upon the release, of relay 315, the right-hand winding of relay 306 energizes over lead 227 in series with the cut-off relay 226 of the called line, and completes a. circuit for relay 318 whereupon ringing current from source 323 is transmitted to the called subscriber. Condenser 319 provides a path over which the ring- ing current is also transmitted to the calling subscriber. When the called subscriber replies, relay 324 energizes and completes the talking connection. Calls to main exchange; connection to idle trunk, Fig. 4. Calling substation No. 13 is connected over relays 206, 208 to an idle linkcircuit in the manner described above for a local call. ' In response to the single digit 0, the marking switch moves to its 10th set of terminals, and, upon the release of relays 308, 309, relays 214, 215<1> energize in series over wiper 219 and lock up. Relay 214 extends the grounded lead 304 to the starting conductor 235, thereby energizing relays 102, 401 of the first idle trunk whilst short-circuiting relay 101. Relay 401 lights lamp 403 individual to the selected trunk. Relay 214 also connects the grounded fourth conductor 229 over leads 231, 232 and 233, 234 to energize connecting relays 103, 105 which lock up to grounded lead 402. Relay 306 is energized over conductors 322, 236, contacts of relays 102, 103, 105 and resistance 109 to disconnect ground from conductor 307, so releasing relays 206, 208. After a short interval, relay 301, the circuit of which was broken bv relay 214, becomes deenergized and the link circuit is restored to normal, the release of relay 214 breaking the short-circuit around relav 101 which now energizes and transfers the starting conductor 235 to conductor 140 leading to the back-contact of a similar relay 101 in the next idle trunk. The cut-off relay 213 remains energized over a circuit comprising contacts of relays 103, 105 and conductors 412, 402. When relays 103, 105 operate, relay 407 energizes in series with the calling substation to lock up a relay 414 and to complete a circuit over grounded conductor 424 and contacts 430, 433 for the line relay 551 at the main exchange. Relay 551 energizes to close the starting circuit of a non-numerical switch or to light a lamp before a manual operator, and in either case, the cut-off conductors are connected to ground and battery respectively, in series with which relay 428 energizes and operates relay 419. Relay 500 energizes over conductor 422 and completes a bridge across the trunk including conductors 421, 424 and a front contact of relay 407. Relay 417 energizes in this bridge circuit and operates relay 418 to maintain relay 419 energized Supervising outgoing calls to particular lines in an automatic main exchange. The impulses transmitted by the calling subscriber are repeated by relay 407 over the previously-traced bridge circuit to operate the main exchange switches in known manner, and are also repeated over lead 411 to a normally-short-circuited relay 502 which energizes in response to each impulse and completes the circuit of the stepping-magnet 504 of the auxiliary switch, Fig. 5. Each row of contacts of this switch contains two sets of ten contacts, each set corresponding to a digit, the sets being separated by a vertical row of intermediate contacts including contact 520. The particular contacts in the bank of wiper 508 which correspond to the first and second digits of called lines for which supervision is desired, are connected to conductor 517, the remaining contacts being left free. Similarly contacts corresponding to selected third and fourth digits in the bank of wiper 509 are als